A conventional scroll compressor is disclosed in Korean Patent Laid-open Publication No. 1998-50613, which will be described with reference to FIG. 1.
As shown, the conventional scroll compressor includes a sealing vessel 1, upper and lower frames 2 and 3 installed at upper and lower parts in the sealing vessel 1, a stator 4 fixedly installed between the upper and lower frames 2 and 3, a rotor 5 inserted into an inner periphery of the stator 4, a drive shaft 6 press fitted into a center of the rotor 5 to pass through a center of the upper frame 2, and an orbiting scroll 7 eccentrically coupled with the drive shaft 7 and having an involute curve wrap 7a formed at an upper end surface of the upper frame 2.
In addition, a stationary scroll 8 is disposed on the orbiting scroll 7 and fastened to a periphery of the upper frame 2 to be engaged with the orbiting scroll 7 to form a compression chamber, and an Oldham ring 9 as an anti-rotation member is installed between the upper frame 2 and the orbiting scroll 7.
In FIG. 1, reference numeral 10 designates a discharge cover, reference numeral 11 designates a check valve housing, reference numeral 12 designates a suction pipe, and reference numeral 13 designates a discharge pipe.
In the conventional scroll compressor, as power is applied, the rotor 5 is rotated inside the stator 4 to rotate the drive shaft 6, and the drive shaft 6 rotates the orbiting scroll 7 in an eccentric manner to a predetermined eccentric distance. At this time, the Oldham ring 9 forces the orbiting scroll 7 to perform an orbital movement about an axial center thereof at a distance spaced apart from an orbital radius.
The orbital movement of the orbiting scroll 7 forms a compression chamber (pocket) between the wraps 7a and 8a of the orbiting scroll 7 and the stationary scroll 8, and the compression chamber moves toward a center thereof by continuous orbital movement such that a volume of the compression chamber is reduced to further compress a coolant gas.
Here, as shown in FIG. 1A, an upper surface of the stationary scroll 8 and a lower surface of the discharge cover 10 have prominence and depression strictures to form a back pressure chamber 14 therebetween. A back pressure hole 14a is formed at one side of the back pressure chamber 14 to be in communication with the compression chamber of the stationary scroll 8, and sealing members (not shown) are disposed at both sides of the back pressure chamber 14.
In the conventional scroll compressor, a coolant gas introduced through a suction port (not shown) formed at the stationary scroll 8 is simultaneously sucked into both ends of a scroll circumference depending on an orbital movement of the orbiting scroll 7 to be trapped in two crescent-shaped pockets (or compression chambers) having the same volume. Then, the volumes of the pockets are continuously reduced to move their centers, thereby compressing the coolant gas.
Since the back pressure hole 14a is formed at a predetermined position of the stationary scroll 8 to be in communication with the back pressure chamber 14, an intermediate pressure of coolant gas enters the back pressure chamber 14 through the back pressure hole 14a to adhere the stationary scroll toward the orbiting scroll 7, thereby preventing the coolant gas from being leaked.
However, the coolant gas can only adjust a back pressure, and an apparatus for performing an oil circulation function such as lubrication still needs to be separately provided. As a result, the apparatus is complicated and its manufacturing process is very difficult.
In addition, since the stationary scroll is axially moved toward the orbiting scroll due to the back pressure, its structure is unstable and its vibration increases.